Sickle guard



Des. 2, W52 E. L. MILLS ETAL 29 9 SICKLE GUARD Filed Aug. 28, 1946 4 Sheets-Sheet l I 30 E INVENTQR-i 40 EIIIIIIIIIIIR 45 y- 35 Mzfls Dec. 2, 1952 E. L. MILLS ETAL SICKLE GUARD 4 Sheets-Sheet 2 Filed Aug. 28, 1946 NV T 5.

Jkmdlfiwzzz ecu 2 3952 E. L. MELLS ETAL SICKLE GUARD 4 Sheets-Sheet 3 Filed Aug. 28, 1946 INVENTOR-S. E'dwa/vd .Zt/l/afi? Jerzrzab 20m Deg 9 1952 E. L. MILLS ETAL 2 6E937 SICKLE GUARD Filed Aug. 28, 1946 4 Sheets-Sheet 4 IN V EN TORS .Z/l/ll' JZWZIwm/ Wwa, 4&7)

Patented Dec. 2, i952 SICKLE GUARD Edward L. Mills and Dennis A. Donahue, Bu-

chanan, Michi, 'assignors to Buchanan Steel Productscorporation, Buchanan, Mich.,a corporation of Michigan Animist Au ust 28, 1946, Serial No. 693,516

2 Claims.

'I'he present invention pertains in-general to cutter guards for mowing machines and," in particular, to improvements in the method of manufacture thereof. "The cutter guards used in mowing machines for cutting grass, grain or thelike, may be forged ofsteel or wrought iron, or may be cast from malleable iron.- Whena casting is employed it is necessary to provide hardened steel inserts, or ledger plates, along the cutting edges of the guard to preclude rapid wearing thereof. This form ofconstruction is expensive and is furthermore objectionable in that the rivets employed'to hold the ledger-plates in place frequently loosen and rise -up,-causingthe cutting knives to be lifted from the ledger plates, which prevents proper functioning of the'knives. Another objection to the use of castings for the cutter guards is that they are brittle and subject to breakage by stones which may be struck by the mowing arm. When forged cutter guards are used, stones or other obstructions may deform the fingers of the cutter guard'b'u't usually will not breakthem. The deformed fingers mayreadily be hammered back into shape, oftentimes without even removing the guard from the mowing arm.

The production of a forged'cutter guard presents certain difficulties which it is one of the objects of the present invention to overcome. One of the difliculties heretofore encountered lies in the formation of the ledger surface of the guard finger. Inasmuch as the ledger surface is normally inaccessible to the forging dies, due to the lip which extends over such surface, it--ha's been difficult to produce a proper cutting edge without first distorting the lip in such manner as to enable the ledger surface to be'reached by the forging dies, after which the lip'is bent back in place. In certain instances the lips have been 'c'onstructed as separate units which are secured tothe body portionsof the guard fingers subsequent to the forging thereof.

--One of the objects of the present invention is to provide an improved cutter guard which is forged in such manner as to produce a cutting edge having therequisite characteristics without thefn'ee'd for'deforming the lipsof the guard fingers during manufacture.

Another object of theinvention is to provide an improved method of manufacturing a forged cutterguardwherein the metal is so worked.

during the forging of the guard as to produce a 'grain structure which makes'the guard exus er u e andv d rabl n hi r s t mtdugh and long-wearing-cutting"edges.

A further object of one form of the invention is to provide a cutter guard which is forged in such manner that the parting line of the forging dies coincides with the cutting edges of the guard, whereby an optimum grain structure is obtained along such cutting edges, and wherein a ledge which extends along the cutting edges is provided to facilitate sharpening thereof.

These and other objects of the invention will be more fully understood upon a perusal of the following specification, when taken in conjunction with the accompanying drawings, wherein:

Fig. 1 is a perspective view of the forged multifinger cutter guard. of the invention in its final form;

Fig. 2 is a longitudinal sectional view on an enlarged scale through one of the fingers of, the guard shown in Fig. 1, taken along the line 22 therein;

Fig. 3 is a sectional view on an enlarged scale through the cutter guard shown in Fig. 1, taken along the line 3-3 therein;

Fig. 4 is a bottom plan view on an enlarged scale of one of the fingers of the guard shown in Fig. 1;

Figs. 5 through 8 are transverse sectional views through one of the finger guards, taken along the lines 55 to 8-8 of Fig. 3; I

Fig. 9 is an assembly view showing the cutter guard attached to a mower arm with the cuttin knives shown in their operating position;

Fig. 10 is a transverse sectional view on an enlarged scale through the assembly shown in Fig. 9, taken along the line Ill-l0 therein; 7

Fig. 11 is a sectional view taken transversely to the finger guards along the line H-l l of Fig. 9; a I

Fig. 12 is a sectionalview similar to Fig. 1-1

Fig. 14 is a sectional View through the forging dies showing the manner in which the forging is completed in two steps;

Fig. 15 is a perspective view of the completed forging prior to trimming thereof;

Fig. 16 i a perspective, view ,of one usedit tr m f r of the dies "Fig. 17 is a perspective view'of the die which prises a plurality of fingers 30 which are joined. together at one end by a bar 32formed integrallytherewith. Each of the fingersincludesa body portion 34 which terminates at one end in a pointed nose 36 of triangular cross sectionand at the other end in a flattened heel 38. The central portion of each finger has a slot to therein forming a ledger surface 42, upon which the cutting knife rests, and forming a lip 44 which extends over the cutting knife. The.1ips 44 protect thecutting knives and alsoserve ,to hold upright the. blades --of grass or grainbeingcut so .as .to prevent-such bladesfrombeing folded over the ledger surfaces in placeof being sheared oif. The cutting knives are generally fiat, consequentlythc slot is preferably wedge-shaped to. provide a gradually increasing clearancebetween the upper surfaces of thecutting knives and the, lips 44 fromthe nose ends of the fingers towardthe heel ends thereof, which assistsin preventing clogging of this space by .thecut grass'or grain.

Itwill be noted that, as shown, the lower side of the slot 40 extends along a ledge 46, which may be formedalong the partingline of the forging dies during. manufacture ofthe guard. One of the purposesof the ledge 46.is to facilitate sharpening of the guard by reducing the amount of metal which, must be removed when the guard is ground along'thesides thereof in a plane substantially perpendicular to theledger surface 42. In instances when such a ledge is not desired, the parting line mayextendalong the portion of the guard which is subsequently removed by sawing to form the slot 45. Astronger shearing edge is obtained with th latter construction, while the optimum grain structure produced along the parting line. during the forging operationsis retained.

A shallow groove 48, which extends transversely to the. fingers 30. along the rear edges of the ledger surfaces 42, is providedin the guard. This groove is suitably dimensioned to receive a knife bar ,to which the cutting knives of the mowing machine are riveted. The bottom surface of the groove 48 includes a cylindrical recess, 50 which provides clearance for the rivets holding the cutting knives to the knife bar. The guard is provided with a plurality of openings 52, each aligned with one'of the'fingers 39 and extending through the heel end thereof. Each of the openings 52 communicates with a wel1,'or cup-shaped depression, 53 formed in the upper side of the guard. The wells 53 are provided to reduce the Weight of the forging and to reduce the thickness of the sections through which the openings 52 are punched.

The bar 32 which joins the fingers of the guard has an S-shaped cross section in order to provide.

angular in form and is ofgradually increasing,

width and depth from thenose ends toward the heel ends of the fingers. From a point substantially in line with the rear edge of the lips 44 and extending to the heel end of the guard, the bottom surface of the fingers is flattened. The portions of the fingers above the ledge or parting line 46 are trapezoidal in cross section and gradually increase in width-and-depth from the nose ends toward, the heel ends of the fingers.

Referring now in particular to Figs. 9 through 12, there is shown a mower arm including a. guard supporting rail 55 having a plurality of studs 54 extending therethrough for attaching the cutter guards. These studs pass through the openings52 in-the cutter guards and have nuts 56 threaded thereon and abutting the flattened surfaceof the guards, thereby rigidly securing them to the rail 55. It will be noted that by forming a plurality of fingers in a single unit, rather'than using individual forgings for each finger, a more rigid mounting is secured in that loosening of anyone of the nuts-56 will :not appreciably affect thev rigidityof the connection of the cutter guard unit to the mower arm. Furthermore, by means of this construction, adequate clearance may be provided between adja-cent units to facilitate ready removalorreplacement of any one unit without interference from adjacent ones thereof. Whenindividual forgings are used for each finger, andonly a single mounting hole is provided therefore, it is necessary to mount the fingers on the mower arm in. abutting relation to. secure adequate rigidity. When this is done, one of 'the fingers may be pinched between adjacent fingers in such manner as to preclude readyremoval of said one finger.

A knife bar 58-, constituting a part of the mower arm, is shown extending along the forward edge of the rail 55 and lying in the shallow grooves 48 provided .in the cutter guards. A plurality ofcutting knives 60 are riveted to the knife bar 58 by means of rivets 62. As previously noted, the lower surface of groove 48 includes azcylindrical recess 50 whichprovidesclearance forthe heads of the rivets 62 on the underside oftheknife bar 58.

The cutting knives 60 are'shaped inthe form of isosceles triangles having, the base angles vcut off normally to the base lines. The knives 'are, positioned side by side with their apexesin line with the corresponding ones of the fingers 30, as shown in Fig. 9, to form a continuous serrated cutting edge. The lower surfaces of the cutting knives rest on the ledger surfaces 42 of the guard fingers. The slanting sides of the knives are beveled to provide cutting .edges which cooperate, with the cutting edges of the fingers to produce a shearing action when the knife bar 58. isreciprocated longitudinally, as illustrated in Fig. 12.

The advantages of the cutter guardmay best be appreciated from a consideration of the method by which it is manufactured, the various steps of which have beenillustrated in Figs; 13 through 20. First, a steel bar 62, of a length determined by the numberv andspacing of the fingers of the guard, is raisedto the required forgingheat. While a barhaving a rectangular cross section is shown, .it, should be understood that bars having differently shaped cross sections, such as circular, maybe employed. The heated bar is then placed over the portion 64 of the lower forgingdie 66. The upper and .lowerdies 66 and 68 are then brought together. under. great pressure to. causethe blank 62.to.be formed. roughly into vthe.desiredlshape. The diesarethen separated and the partially completed forging is rotated through 180 degrees into position to be acted upon by the portions 12 and 12a. of the dies 66 and 68, as has been illustrated by the arrow in Fig. 14. The dies are then again brought together under pressure to complete the guard forging 12.

During the forging operation, the greater part of the metal in the blank will be forced into the depressions in the die which correspond to the finger portions of the guard, but a portion of the metal will flow between the surfaces of the dies to form a web 74 which is commonly called the flash.

It should be noted that the metal is forced to fiow principally lengthwise of the finger portions of the guard, but is also forced to flow transversely to the finger portions along the parting line. The grain structure is therefore such as to impart maximum strength to the body portions of the guard and at the same time to produce a region along the parting line which is ideally suited to be formed into a cutting edge.

While the forging 12 is still hot, it is placed over a shearing die 76 which is shaped to conform to the outline of the finished form of the cutter guard, as illustrated in Fig. 17. An upper shearing die 76, which complements the lower die 16 and is recessed to fit over the forging 72, is then lowered under pressure to trim the flash 14 from the forging 12. The portion 74 trimmed from the forging is shown in Fig. 18.

The openings 52 for receiving mounting studs are next punched in the cutter guard at the heel end thereof, as shown in Fig. 19. The wells, or cup-shaped depressions 53, which communicate with these openings, are formed during the forging operation. After the punching operation, slots are cut in the fingers of the guard to receive the cutting knives of the mowing machine. The slots are out with a saw, or milling cutter, 80 having straight sides. During the forging operation, the metal is stressed in such manner that the lip portion 44 of the guard fingers springs away from the body portion 34 at the time that the slots are cut. Thus a wedge-shaped slot results, although the slot is out with a straight-sided saw or milling cutter. If more taper is desired, the lips may be further formed from the ledger surfaces after the sawing operation.

The sawing operation produces a true ledger surface 42 which requires no further finishing. As the side of the body portion 34, or of the ridge 46, which may be left on the forging when it is trimmed in one form of construction, is smooth and straight when the forging leaves the trimming dies, a sharp cutting or shearing edge is formed along the junction between the ledger surface 42 and the side of the body portion, or of ridge 46, when slots 4|] are cut in the guard. It is therefore necessary to grind the cutting edge of the guard during manufacture. After the guard has been placed in service and becomes dull, the side of the body portion, or of ridge 46, may be ground to restore the sharpness of the cutting edge. As the width of ridge 46 is relatively small, the grinding may be accomplished quite rapidly when the form of construction illustrated is employed.

After the slots have beencut in the guard fingers, the cutter guard is subjected to heat treatment to harden the cutting edges. Al-

though the heat treatment may be confined to the region adjacent to the cutting edges, if desired, it is preferred to case harden the whole unit so as to produce a hard abrasion-resisting surface while leaving the core in its original tough and non-brittle state.

It should now be apparent that, by reason of the novel method of manufacture described herein, a cutter guard has been provided which is forged of steel in one piece in such manner as to obviate the difficulties heretofore encountered in the forging of such guards; namely, by sawing a slot in the guard finger along the parting line a tough and durable cutting edge is provided without any need for deforming the guard lip during manufacture.

By forging a multi-finger guard from a bar extending transversely to the fingers, the metal is forced to flow alon lines which impart maximum strength and toughness to the guard fingers. At the same time, the flow lines are altered along the parting line, where the cutting edge is subsequently formed by sawing, so as to impart the desired long-wearin characteristics to such cutting edge.

While a particular embodiment of the invention has been shown by way of illustration, it is obvious that various modifications may be made without departing from the invention in its broader aspects, and therefore it is the aim of the appended claims to cover all such modifications as fall within the true spirit and scope of the invention.

The invention is hereby claimed as follows:

1. A cutter guard for use in a mowing machine, said guard being formed of forged steel, said guard having an elongated body portion having a ledger surface along a portion thereof and a lip overlying the same, the guard body portion being provided at its opposite sides and along the margins of said surface with cutting edges, said guard body portion having at its opposite sides a parting line region resulting from a forging operation and having the said cutting edges lying in said region, whereby said guard body portion will have grain lines running longitudinally interiorly thereof and transversely thereof at said cutting edge portion.

2. A cutter guard as claimed in claim 1, wherein at least a portion of said region extends laterally from the guard body portion to provide ledges on which the said cutting edges are disposed.

EDWARD L. MILLS. DENNIS A. DONAHUE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date D. 32,965 Shepler July 17, 1950 55,074 Dutton May 29, 1866 65,977 Whiteley et a1. June 18, 1867 121,261 Sweet Nov. 28, 1871 209,465 Curtis Oct. 29, 1878 258,166 Van Ness et al. May 16, 1882 356,357 Folliott Jan. 18, 1887 356,974 Bagaley Feb. 1, 1887 1,610,401 Ward Dec. 14, 1926 2,039,012 Lindberg Apr. 28, 1936 2,226,583 Rionning Dec. 31, 1940 

